At best Rudy has even odds with McCain. Romney is a longshot. That said, I expect McCain will be the GOP nominee. Recent history strongly suggests just that.
1976
Reagan vs. Ford, Ford overcomes
1980
Bush vs. Reagan, Reagan overcomes
1988
Dole vs. Bush, Bush overcomes
1996
Dole coronated
2000
McCain vs. Bush, Bush overcomes
2008
Giuliani vs. McCain, undecided
I suggest and hope neither.